Lecture Notes: Conservation of Angular Momentum in Helicopters

Introduction

• Speaker: Jacob
• Topic: Conservation of Angular Momentum and its application in helicopter maneuvering flight.
• Context: Effects typically experienced during aggressive helicopter maneuvers, not in standard flight patterns.

Conservation of Angular Momentum

• Definition: Angular momentum of a rotating body remains constant unless acted upon by external forces.
• Relation to Newton's Law: Variation applied to rotating bodies.
• Application to Helicopters: Rotor blades try to conserve their angular momentum.

Coriolis Effect

• Definition: Tendency of a rotating body to increase velocity as its center of gravity moves closer to the axis of rotation.
• Relation to Angular Momentum: Used interchangeably in this lecture.

Helicopter Flight Mechanics

• Maneuvering Flight Effects:
  • Increased G loading affects rotor system.
  • Rotor begins to cone (increasing coning angle).
  • Blade diameter shrinks as coning occurs.
  • Center of gravity shifts closer to the axis of rotation.
  • Rotor RPM changes as a result.

Comparison Examples

• Figure Skater Analogy:
  • Arms closer = increased RPM.
  • Arms extended = decreased RPM.
• Racecar on Track:
  • Shorter track loop = more revolutions per minute while maintaining the same speed.

Engine Control System in Helicopters

• Function: Maintains rotor RPM.
• Response to RPM Changes:
  • Decrease fuel flow when rotor RPM increases.
  • Increase fuel flow when rotor RPM decreases.

Potential Issues and Considerations

• Rapid Rotor Fluctuations:
  • Can lead to overspeeding or underspeeding of rotors.
  • Possible over-torqueing if engine fuel adjustments aren’t timely.
• Pilot Considerations:
  • Awareness of rotor RPM and torque fluctuations is crucial.
  • Anticipate changes with collective application to avoid exceeding limits.

Conclusion

• Key Takeaway: Rotor blades aim to maintain momentum; G loading causes RPM changes.
• Impacts on Aircraft: Potential for over-speed, under-speed, or over-torque conditions.
• Pilot Advice: Understanding rotor RPM changes is critical for safe maneuvering.

Closing

• Reminder: Understanding rotor dynamics is essential for flight safety.
• Call to Action: Like and subscribe for more helicopter lessons.
• Presented by: Jacob, "Helicopter Lessons in Ten Minutes"